Papers by Author: Wladek Walukiewicz

Abstract: ZnTe solar cells with homojunction and heterojunction structures have been developed. Homojunction was fabricated by thermal diffusion of Al into p-ZnTe, and the effect of the diffusion temperature on the photovoltaic (PV) properties was investigated. The highest efficiency was obtained by lowering the diffusion temperature and using p-ZnTe substrate with a low hole concentration. For the heterojunction solar cell, n-ZnO/i-ZnTe/p-ZnTe structure was fabricated, and PV properties were characterized.

Abstract: This paper describes Transmission Electron Microscopy studies of the structural changes of GaN1-xAsx alloys grown by Molecular Beam Epitaxy at low temperatures on Al2O3 substrate. We found that by lowering the growth temperature increasing amount of As can be incorporated in GaN1-xAsx forming a single phase alloy. For the low As content a columnar growth of wurtzite structure is observed but for increasing As in the range of 0.170.75 the layer becomes amorphous. Increase in Ga flux at low growth temperature (about 200°C) leads to columnar alloys with As content >75% with a cubic structure. In addition to the structural changes monotonic change of the band gap is also observed with the As content in the alloy. The amorphous alloy is stable up to annealing at temperatures not higher than 600°C. Annealing at higher temperature leads to phase separation of GaAs:N and GaN:As confirmed by Z-contrast electron microscopy.